Study aim: Efficacy of Favipiravir in managemant of patient with COVID-19 Design: This is a double blind clinical trial study in phase 3 with 114 patients with COVID19 that randomly devided into 2 groups. Settings and conduct: This is a double blind clinical trial study with114 patients with positive PCR for COVID19 that have referred to Khansari and Valiasr hospital and they are in subgroup 3 of hospitalization.They will be devided into 2 groups (Favipiravir and control)randomly. Participants/Inclusion and exclusion criteria: Inclusion criteria: Patients with COVID19 referred to Khansari and Valiasr hospital Patients with COVID19 in subgroup 3 of hospitalization(i.e SPO2 less than 80% or PaO2 less than 60 CmH2O, severe respiratory distress and respiratory rate more than 34 per minute, instable hemodynamic, acid base disturmance, similar to moderate to severe cases) Exclusion criteria: Pregnancy Drug reaction Deterioration of symptoms after drug usage Renal failure manifestation Heart failure manifestation Intervention groups: Patients in Favipiravir group will be received Favipiravir tablet for 7 days. Patients in control group will be received placebo (flour tablet) for 7 days. Main outcome variables: severity of COVID19